This invention relates to internal combustion engines and is particularly concerned with a fuel supply system arranged to provide increased efficiency in the delivery of fuel to the engine.
The invention is applicable to engines of various kinds having a combustion chamber and having fuel inlet porting for delivering fuel either directly or indirectly to the combustion chamber, and certain aspects of the invention are applicable to engines of a variety of types, including engines with cylinders and reciprocating pistons therein, and engines in which the combustion chamber accommodates a rotary type of piston. Although the invention is applicable to a broad range of reciprocating piston and cylinder types of engines, the invention is herein illustrated and described as applied to a two-cycle internal combustion engine of the kind commonly employed in motorcycles, power saws, lawn mowers and other appliances and devices.
Still further, while the invention may be employed in association with fuel intake and valving systems of various kinds, the invention is particularly applicable in engines in which reed valves are employed in the fuel intake system, and the invention is, therefore, herein illustrated and described in connection with two-cycle engines employing reed valves.
In various types of engines above referred to, fuel intake porting is provided and the fuel supply means includes passage walls defining a fuel passage communicating with the inlet porting and having valve means in the passage to control the flow of fuel in the passage.
It is quite common, especially in two-cycle engines, to employ reed valves in the fuel supply passage in a region near the intake porting; and in order to accommodate the reed valve mechanism, the passage leading to the intake porting in the region of the reed valves must be of substantial cross-sectional area. This is particularly true where it is desired to employ a number of reed valves so as to maximize the fuel intake.
However, the portion of the fuel supply passage extending upstream to the carburetor or other means for introducing the fuel into the system, commonly has a cross-sectional area considerably smaller than the cross-sectional area in the region of the reed valves. It is of advantage in connection with the operation of the carburetor to avoid having a fuel delivery passage of excessive cross-sectional area, because for a given quantity of fuel and air, the rate of flow would be retarded; and in the operation of carburetors generally, the quantity of air and fuel intermixed in the carburetor is more accurately and reliably established where the velocity of delivery of the mixture is relatively high. It is, therefore, of significance in the operation of the carburetor to employ a delivery passage of relatively small cross-sectional area.
Since it is of importance to provide a space having a relatively large cross-sectional area in order to accommodate the desired reed valves and since it is desired to provide a carburetor delivery passage which is of relatively small cross-sectional area, the flow of the fuel from the passage of relatively small cross-sectional area into the space of relatively large cross-sectional area has heretofore resulted in substantial reduction in the velocity of fuel fed in the region of the reed valves. This is undesirable for several reasons, including the fact that a higher velocity in the region of the reed valves more effectively operates the reed valves; and in addition, the fluctuation in velocity of the incoming fuel mixture represents a waste of kinetic energy because of the deceleration of the fuel flowing to the cylinder.